In battery modules for electric cars or hybrid cars, a plurality of single cells are lined up, each single cell being constituted by a flat main body in which a power generating element is provided, and positive and negative electrodes. The plurality of single cells is connected in series or in parallel to each other by electrodes of adjacent single cells that are connected by connecting members (busbars).
JP-A-2000-149909 discloses a battery wiring module that is configured such that a large number of busbars are incorporated into a substrate section made of a synthetic resin by insert molding. This battery wiring module is mounted to a single cell group, and single cells are connected to each other by inserting electrode bolts of the single cells through electrode holes formed in the busbars, and tightening the busbars with nuts.